Laboratory Write-ups

Your Name: Barbara J. Shaw

Laboratory Title: Dry Ice Inquiry Investigation: The Scientific Method

Lab Objectives:

  • Students will engage in the scientific method (scientific inquiry)
  • Students will make observations of dry ice
  • Students will read about dry ice to get more information about this chemical
  • Students will ask questions about their observations or reading of dry ice
  • Students will design an experiment to answer their question
  • Students will make a prediction of the outcome from their experiment (the hypothesis)
  • Students will collect data on dry ice
  • Students will analyze those data and develop a graph of the results
  • Students will answer their question and either accept or reject their prediction
  • Students will write a paper or make a poster about their experiment

Benchmark(s) Addressed:

Physical Science

CCGMatter: Understand structure and properties of matter.

SC.05.PS.01Identify substances as they exist in different states of matter.

SC.05.PS.01.01Distinguish among solids, liquids, and gases.

SC.05.PS.01.02Identify unique properties of each state of matter.

CCG Matter: Understand chemical and physical changes.

SC.05.PS.02Describe the ability of matter to change state by heating and cooling.

SC.05.PS.02.01Recognize that heating and cooling cause changes in states of matter.

SC.05.PS.02.02Identify changes in states of matter seen in the environment.

CCG:Force: Understand fundamental forces, their forms, and their effects on motion.

SC.05.PS.03Describe and compare the motion of objects.

SC.05.PS.03.01Recognize and describe the motion of an object in terms of one or more forces acting on it.

CCG Energy: Understand energy, its transformations, and interactions with matter.

SC.05.PS.05Identify forms of various types of energy and their effects on matter.

SC.05.PS.05.01Identify various forms of energy including heat, light, sound, and electricity.

SC.05.PS.06Describe examples of energy transfer.

SC.05.PS.06.01Identify the direction of heat transfer on a diagram showing objects at different temperatures.

SC.05.PS.06.03Identify examples of energy transfer in the environment.

Earth and Space Science

CCGThe Dynamic Earth: Understand the properties and limited availability of the materials which make up the Earth.

SC.05.ES.01Identify properties and uses of Earth materials.

SC.05.ES.01.01Recognize that Earth materials are used in different ways based on differences in their physical and chemical properties.

SC.05.ES.01.03Recognize that the supply of resources is limited, and that resources can be extended through recycling and decreased use.

CCG: The Universe: Describe natural objects, events, and processes outside the Earth, both past and present.

At this time there are no Standards associated with this CCG

Scientific Inquiry

CCG Forming the Question/Hypothesis: Formulate and express scientific questions or hypotheses to be investigated.

SC.05.SI.01Make observations. Ask questions or form hypotheses based on those observations, which can be explored through scientific investigations.

CCGDesigning the Investigation: Design safe and ethical scientific investigations to address questions or hypotheses.

SC.05.SI.02Design a simple scientific investigation to answer questions or test hypotheses.

CCGCollecting and Presenting Data: Conduct procedures to collect, organize, and display scientific data.

SC.05.SI.03Collect, organize, and summarize data from investigations.

CCGAnalyzing Data and Interpreting Results: Analyze scientific information to develop and present conclusions.

SC.05.SI.04Summarize, analyze, and interpret data from investigations.

Mathematics
Calculations and Estimations
CCG:Numbers: Understand numbers, ways of representing numbers, relationships among numbers, and number systems.
MA.05.CE.01 Order, model, and compare common fractions, decimals and percentages.
CCG:Computation and Estimation: Compute fluently and make reasonable estimates.
MA.05.CE.14 Use referent numbers and rounding to estimate the magnitude of calculations with decimals.
Statistics and Probability
CCG:Statistics: Select and use appropriate statistical methods to analyze data.
MA.05.SP.01 Compare two related sets of data using measures of center (mean, median, and mode) and spread (range).
CCG:Collect and Display Data: Formulate questions that can be addressed with data and collect, organize, and display relevant data to answer them.
MA.05.SP.03 Design investigations to address a question and recognize how data collection methods affect the nature of a set of data.
MA.05.SP.04 Understand basic concepts of sampling (e.g., larger samples yield better results, the need for representative samples).
MA.05.SP.05 Represent and interpret data using tables, circle graphs, bar graphs, and line graphs or plots (first quadrant).
MA.05.SP.06 Compare different representations of the same data and evaluate how well each representation shows important aspects of the data (e.g., circle and bar graphs, histograms with different widths).
MA.05.SP.07 Evaluate the appropriateness of representations of categorical and numeric data (e.g., categorical: types of lunch food; and numerical: heights of students in a class).
CCG:Data Analysis and Predictions: Develop and evaluate inferences and predictions that are based on data.
MA.05.SP.08 Analyze data from tables and bar graphs using mean, median, mode, and range, and draw conclusions.

CCG:Modeling: Use mathematical models to represent and understand quantitative relationships.

MA.05.AR.07 Identify or describe a situation which may be modeled by a given graph.

Measurement

CCG:Units and Tools: Understand measurable attributes of objects and the units, systems and processes of measurement.

MA.05.ME.01 Using estimation, convert from a measurement expressed using one unit within a system to one using a comparable unit within the other system (e.g., inches to centimeters).

MA.05.ME.02 Understand that measurements are approximations and understand how differences in units and tools affect precision.

CCG:Direct & Indirect Measurement: Apply appropriate techniques, tools, and formulas to determine measurements.

MA.05.ME.03 Know common referents for Fahrenheit and Celsius temperatures (e.g., freezing point, boiling point).

MA.05.ME.09 Compare and contrast the formulas for area of rectangles, related triangles, and parallelograms.

MA.05.ME.10 Estimate and measure volume of a rectangular solid using unit cubes.

MA.05.ME.11 Use referents for metric measurements to make estimates of length, weight, and volume and evaluate the reasonableness of the estimate (e.g., height of teacher estimated in height of student lengths).

Mathematical Problem Solving

CCGConceptual Understanding: Select, apply, and translate among mathematical representations to solve problems.

MA.05.PS.01 Interpret the concepts of a problem-solving task and translate them into mathematics.

CCGProcesses and Strategies: Apply and adapt a variety of appropriate strategies to solve problems.

MA.05.PS.02 Choose strategies that can work and then carry out the strategies chosen.

CCGVerification: Monitor and reflect on the process of mathematical problem solving.

MA.05.PS.03Produce identifiable evidence of a second look at the concepts/strategies/calculations to defend a solution.

CCGCommunication: Communicate mathematical thinking coherently and clearly. Use the language of mathematics to express mathematical ideas precisely.

MA.05.PS.04 Use pictures, symbols, and/or vocabulary to convey the path to the identified solution.

CCG:Accuracy: Accurately solve problems that arise in mathematics and other contexts.

MA.05.PS.05 Accurately solve problems using mathematics.

Materials and Costs:

List the equipment and non-consumable material and estimated cost of each

Item $

  • Cooler (1) 15.00
  • Leather gardening gloves (16 gloves @ $4.00 ea) 64.00
  • Plastic spoons (can be recycled spoons) 2.00
  • Craft sticks (30) 2.00
  • Tongs (15 @ $1.00 at Dollar Store) 15.00
  • Hammer (1) 5.00
  • Plastic cups (30) 4.00

Estimated total, one-time, start-up cost: 110.00

List the consumable supplies and estimated cost for presenting to a class of 30 students

Item $

  • Dry ice (15 pounds @ $1.59/lb – *Baskin and Robbins) 23.85

Estimated total cost each year (no including replacement items): 23.85

*Dry ice is easiest to access, but most expensive at Baskin and Robbins. Other places to check include grocery stories, hunting supply stores during hunting season.

Time:

Initial prep time:purchase permanent materials ~ 30 minutes

Preparation time:purchase dry ice ~15 minutes

Instruction time:2 – 6 hours (can be subdivided into 45-60 minute increments over several days, or taught in a single, intensive day).

Clean-up time:~15 – 30 minutes

Assessment: (at end of lab)

Background:

Dry ice is frozen carbon dioxide, a normal part of our earth's atmosphere. It is the gas that we exhale during respiration, and the gas that plants uptake in photosynthesis. It comprises about 0.038% of the total gases in the air. The other gases in our atmosphere are 78% nitrogen, 20.95% oxygen, 0.93% argon, and the balance composed of trace gases including water vapor.

Carbon dioxide is used in a wide variety of products, for example, it is gas added to soda pop to make it fizz. Dry ice is particularly useful for freezing, and keeping things frozen because of its very cold temperature, -78.5°C (-109.3°F). It is widely used because it is simple to freeze and easy to handle using insulated gloves. Dry ice changes directly from a solid to a gas -sublimating - in normal atmospheric conditions without going through a wet liquid stage.

The first step in making dry ice is to compress carbon dioxide gas until it liquefies, at the same time removing the excess heat. The C02 gas will liquefy at a pressure of approximately 870 pounds per square inch at room temperature. The pressure is reduced over the liquid carbon dioxide by sending it through an expansion valve into an empty chamber. The liquid will flash, with some turning into gas causing the remainder to cool. As the temperature drops to -78.5°C, the temperature of frozen CO2, some of it will freeze into snow. This dry ice snow is then compressed together under a large press to form blocks or extruded into various sized pellets. Dry ice is much heavier than traditional ice, weighing about double.

Atmospheric pressure is the pressure at any point in the Earth's atmosphere. In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point. Low pressure areas have less atmospheric mass above their location, whereas high pressure areas have more atmospheric mass above their location. Similarly, as elevation increases there is less overlying atmospheric mass, so that pressure decreases with increasing elevation. A column of air 1 square inch in cross section, measured from sea level to the top of the atmosphere, would weigh approximately 14.7 lbf (pound-force). A 1m² (11sq ft) column of air would weigh about 100 kilonewtons (equivalent to a mass of 10.2 tons at the surface). This to compare to the 870 lbf needed to “force carbon dioxide gas into a liquid phase.

CO2 is a greenhouse gas, which means it absorbs light at infrared wavelengths. An increase in the concentration of this gas would, some scientists believe, cause an increase in the atmosphere's average temperature. The high concentration of CO2 in the atmosphere of the planet Venus is said to contribute to that planet's high average temperature. The ice caps on Mars are primarily dry ice!

At normal atmospheric pressure on this planet, frozen CO2 doesn't melt into a liquid, but rather evaporates directly into its gaseous form (hence the name dry ice). This process is called sublimation. All of the experiments below rely on this property of dry ice. 1 pound of dry ice, when it "sublimes" (turns to gas) will produce 250 liters of gas at atmospheric pressure, enough to fill 125 2-liter bottles. That's a lot of gas!

Scientific Method

I teach the scientific method as 10 steps. I have found this to be very effective. The benchmarks are written as 4 steps, but they underplay communication aspect of this method. This emphasizes it.

1.Make observations – This is a very intellectual way of saying, let’s play with this so we can really understand the properties that we will be exploring formally in an experiment. You will be infinitely rewarded with enthusiasm for this entire process when you utter the words, “That means play with it!” At this point, don’t go into the safety issues. Focus on the steps. Safety will be addressed just before the dry ice is passed out each time.

2.Ask questions – During the play session, questions invariably come up. (Why did that happen? I wonder if…) The class needs to be aware that they are asking them, and jot them down. There should be plenty of room for the students to jot down their questions, make drawing of their ideas, etc. There needs to be some thought as to the question and the hypothesis. If the question is too broad or complex, then no one experiment could answer it in one experiment. The question needs to be one simple question that is easily testable because it has some type of measurement in it. How and why questions are too broad. If the class comes up with a how or why question, you can use it to narrow down and find a testable question. For example, “How can dry ice sublimate faster?” is too broad. You can guide your students into thinking of two different mediums. The question would then change to “Which will make dry ice sublimate faster, 70ºF room temperature air or 70ºF temperature water? (Simple, measurement of time, easily testable) As the class is “observing” the dry ice, listen for these questions. Since this is an abbreviated version of the scientific method, select a question that is easily testable in your 1.5 hours.

3.Research – When I get to this point, I try to read everything that has ever been written on the subject, or closely related subjects. The question may already have been tested. I can then choose to retest, if I feel that there may be factors that weren’t analyzed in the initial study, or I can use that research to go further with my experiment. In that case, I would need to revise my question. For your students, discuss how dry ice is made, get ideas different types of experiments and so on. You can present information pertinent to their specific question.

4.Refine question and formulate hypothesis – The class needs make a prediction. The prediction is the hypothesis. In the example above, the hypothesis could be, “Dry ice will sublimate faster in 70ºF temperature water than in 70ºF temperature air.” Another example, “Will dry ice gas explode if it were by a flame?” The hypothesis would be “An explosion will occur when a flame is immersed in the dry ice gas (CO2).”

5.Design experiment (develop experiment) – This step requires creative thinking. Your students need to design an experiment that actually can help to answer the question they asked. Will the results support or reject the hypothesis. One of the hardest concepts for students to understand in any scientific experiment is that data that proves the hypothesis wrong is just as important as an experiment that supports a hypothesis. Knowing that this does not work is sometimes more important in trying to understand the very nature of what we are studying. Back to the students who want to see if carbon dioxide gas will explode in the presence of a flame would find out that their hypothesis is rejected. In fact, carbon dioxide will put out a flame. Look at the school fire extinguisher. The gas in it is none other than carbon dioxide! Your class would learn something incredible – not all gasses are volatile (a very common misconception). The class needs to be very detailed in how they will conduct their experiment. You also need to be aware of the limitations of the supplies that you have brought. It is okay to guide your class. You can record the plan on the blackboard. For example:
Dry ice will sublimate faster in 70ºF temperature water than in 70ºF temperature air.
2 – 1” cubes of dry ice
2 plastic cups
thermometer
water
watch or timer
scale (could use a postage scale)

  • Run tap water and hold one of the thermometers in the stream of water. Adjust the water until the water is the same temperature as the air (70ºF)
  • Fill the jar with water about ¾ full
  • Weigh the dry ice for 2 pieces as close to similar size, shape and mass. Record weight.
  • Put one piece of dry ice in each of the two jars.
  • Place the dry thermometer in each jar without the water, keeping it as far away from the dry ice as possible
  • Place the wet thermometer in the jar with the water, keeping it as far away from the dry ice as possible.
  • Record the temperature and approximate size of each piece of dry ice every minute.
  • When one of the pieces of dry ice is completely sublimated, note the time, the size of the other piece of dry ice, and end the experiment.

6.Collect data (the experiment) – The class working with their partner, following the step-by-step directions they outlined, do the experiment.

7.Analyze data – Use all the partners’ data as a class. Data is collected in numbers. Even when collecting data on behavior, the collection is number of times, length of time, etc. anything that can be translated into number. Then, all those numbers are crunched in a wide variety of ways, for example statistics, calculus, or geometry. This part of the scientific method quantitatively analyzes the data collected. Your students may be able to use some statistics, if they have had a unit on it, or though the use of graphs. The data is also analyzed qualitatively (describing it).

8.Draw conclusions – Was their hypothesis supported or rejected? The team also tries to figure out why. Then they write up their conclusions. They will need to include their data in the report.